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Avalanche Forecast

Dec 23rd, 2011–Dec 24th, 2011
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

Confidence

Fair - Intensity of incoming weather is uncertainfor the entire period

Weather Forecast

Saturday: 20-30cm of snow - moderate to strong southwest winds - freezing level at 1000mSunday: 8-15cm of snow - moderate southwest winds - freezing level at surfaceMonday: moderate snowfall - Moderate winds from the south - freezing level at surface

Avalanche Summary

Limited observations at this time. Expect widespread natural avalanche activity throughout the weekend for forecast wind and snow.

Snowpack Summary

Earlier this week the forecast region got slammed by snow, wind and fluctuating freezing levels. Including the 20cm that fell on thursday night, the southern part of the region has received over a meter of new snow over the past week (Kasiks, Terrace areas). Locations to the north are seeing less (Stewart up to 60cms). This new snow has been blown around by extreme-strong southwest winds creating stiff wind slabs on lee slopes. The winds have switched from the SW to the NW. This switch was short lived through Wednesday, but may have formed new wind slabs on SE - S facing slopes. This makes the wind slab problem even trickier to predict. In addition to the more obvious direct-action storm instabilities that are expected with the forecast weather, local avalanche professionals have some other concerns: Surface hoar that formed during the winter solstice sits approximately 30cm below the surface and will become more reactive with more wind and snow. As well, the crust-facet combo (extends up to alpine elevations in the south and around 1000m in the north) from the early december dry-spell sits about 135cm below the surface and has not gone away . Any avalanches on this layer would be highly destructive and is probably waiting for the right load or trigger. The mid and lower snowpack are settled out and strong. Snowpack depths in the Kasiks, Terrace areas are reaching the 300cm mark. Further north Smithers, Bear Pass depths are ranging from 180-250cms.

Avalanche Problems

Wind Slabs

Strong winds will form large wind slabs on cross-loaded and lee slopes. They will be touchy and destructive in many parts of the region.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Storm Slabs

Heavy snowfall amounts have created and will continue to create storm slabs at all elevations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Persistent Slabs

The crust that developed during the early December dry spell may awaken with increased loads or a significant trigger (cornice fall, trenching sled track). Avalanche activity on this layer would be highly destructive.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 5